This invention relates to an improved heat exchanger tube and, in particular, to a heat exchanger tube having a dense population of spine-like fins mounted thereon in a spiral configuration.
More specifically, this invention relates to a heat exchanger tube made up of a primary tubular element for carrying a heating or cooling medium and a secondary heat transfer surface spirally wound about the tube having a multitude of thin spine-like fins protruding therefrom for transferring energy between the heating or cooling medium and air passing over the tube. The spines or fins are separated from each other throughout their entire length by an air gap that increases progressively from the base of the heat transfer surface to the tip of each spine. The tube's resistance to air is thus minimized making the tube well suited for use in air conditioning equipment or the like. The structure of the spine finned tube also minimizes the possibility of condensate freezing upon the tube. Moisture forming on the tube is directed downwardly by the spines and, because of the surface tension involved, is rapidly released by the tube. It should be further noted that a single section of wrapped fin tube can be conveniently formed into any number of shapes to produce a heat exchanger of almost any desired geometry that is easy to assemble and which eliminates costly components, such as tube return bends or the like, normally found in exchangers of a more conventional construction, and which are soldered or brazed into position.
Although, as pointed out above, many advantages are associated with a wrapped fin tube, this type of device has not as yet been widely utilized in the industry primarily because of the many difficulties associated with tube fabrication. This is particularly true where the primary and secondary tube elements are formed of aluminum or other materials that are difficult to join.
Heretofore, the secondary spine finned element has been joined to the primary tubular element by either a metal bonding process, such as welding, soldering, brazing, or the like, or adhesive bonding. The metal bonding techniques generally require special, relatively expensive, equipment to join the components. Furthermore, most metal-to-metal bonding processes invariably expose the components to high temperatures which can warp or thermally damage the parts. Adhesive bonding, on the other hand, is typically achieved by covering the outer surface of the primary tubular element with an adhesive coating and then wrapping the secondary fin element over the coated tube. A thermal resistance, i.e., the adhesive layer, is thus introduced into the critical region between the fin strip and the exchanger tube through which energy in transit must pass. Generally, this region represents a bottleneck in the heat transfer system and any impediment to passage of energy through this region will, of course, reduce the efficiency of the heat exchanger tube.